The invention relates generally to the reprocessing of spent nuclear fuel assemblies and, more particularly, to a method and apparatus for shearing spent nuclear fuel assemblies of the type comprising an array of elongated fuel pins disposed within an outer metal shroud. It was made in the course of, or under, a contract with the United States Department of Energy.
Reprocessing of spent fuel assemblies from boiling water reactors (BWR) and pressurized water reactors (PWR) to recover fuel values is accomplished by a process known as the shear-leach process wherein the fuel assemblies are sheared or cut into short segments and the recoverable fissile and fertile materals leached out of the sheared segments with nitric acid. Apparatus to accomplish the shearing part of the shear-leach process is generally known as a fuel-bundle shear. Although fuel-bundle shears have been developed and routinely used in connection with the reprocessing of BWR and PWR fuel assemblies, fuel assemblies developed for use in the liquid metal fast breeder reactor (LMFBR) present special problems in connection with the shearing operation. For example, fuel assemblies used in the LMFBR use a heavy 0.120-inch thick stainless steel shroud to provide a channel for the sodium coolant and to act as a support structure for the fuel pins while 0.031-inch thick shrouds are found in PWR and BWR reactors. Such heavy shrouds are more difficult to shear and can cause disruptions in post-shear processing if not uniformly sheared into small uniform pieces. In addition, spent LMFBR fuels will display higher radioactivity and decay heat emission than spent fuels from conventional pressurized water and boiling water reactors and will require the highest degree of system reliability throughout remotely operated fuel reprocessing operations.
These and other unique problems associated with the fuel assemblies used in the LMFBR require that the product from the shearing mechanism be small and uniform to avoid blockage during subsequent chemical processing.
It is, accordingly, a general object of the invention to provide a method and apparatus for shearing spent fuel assemblies which yield uniform sheared segments of relatively small size.
Another object of the invention is to provide a method and apparatus suitable for shearing LMFBR fuel assemblies having a heavy shroud.
Other objects of the invention will be apparent upon examination of the following written description of a preferred embodiment of the invention and the accompanying drawings.